1. Field of the Invention
This invention relates to stacking of wood such as lumber and plywood for drying or other purposes and more particularly, to an automatic stick laying apparatus for positioning spacing sticks on stacked tiers of lumber to provide proper ventilation between the layers of lumber.
At a very early date it became obvious that lumber must be cured prior to use in order to avoid, or at least minimize, warping due to drying. In the early sawmill days "green" lumber was stacked in "ricks" which defined an inverted "V" configuration, where it was air-dried to reduce the moisture content and provide reasonably straight boards for building purposes. With the development of modern sawmills, the rate of processing and drying or curing of "green" lumber increased to the point that it became impractical and unprofitable to stack lumber in this "rick drying" fashion and other techniques were devised to accomplish this purpose. The lumber is now stacked for kiln drying or air drying and the stacking is preferably accomplished in multiple rows and layers by inserting between each tier or layer of boards a number of small spacing sticks which keep the layers spaced and provide ventilating passages through the stack to expose both the upper and lower surfaces of the boards in the stack to the drying air. This procedure serves the purpose of processing a large number of boards of selected size in a relatively short period of time, thereby providing more favorable sawmill economics.
2. Description of the Prior Art
The stacking of lumber has been accomplished by varying apparatus and techniques in modern times. U.S. Pat. No. 2,928,559, dated Mar. 15, 1960, to D. E. Mosely, details a "Lumber Stacker" which includes a mechanism for receiving boards from a source of supply, gathering the boards in layers and depositing the layers on the stack being formed and further including a mechanism for inserting multiple spacing sticks between each layer as the lumber is stacked, to space the layers in tiers. U.S. Pat. No. 3,352,434, dated Nov. 15, 1967, to W. H. Zuercher, details a "Stick Placer Apparatus". The device features a constant feed of sticks on slats from a removable cartridge to insert the stick between successive layers of a stack of lumber and space the lumber for drying. A "Lumber Spacer and Stick Layer" is detailed in U.S. Pat. No. 4,229,133, dated Oct. 21, 1980, to Charles L. Johnson. The lumber spacer automatically separates lumber in parallel alignment, drops spacer sticks on top of the stacked lumber and subsequently stacks more lumber on top of the spaced sticks. U.S. Pat. No. 4,360,303, dated Nov. 23, 1982, to Alpo Rysti, details a "Method and Apparatus for Locating Spacer Strips Between Layers of Timber Packages". The device positions spacer strips between vertically adjacent layers of timber by locating multiple spacer strips supported by distribution members over the top layer of the timber package and activating multiple depressers, which are operatively associated with a frame structure, downwardly to engage respective spacer strips and guide the strips into position on the top layer of the timber package. U.S. Pat. No. 4,610,360, dated Sep. 9, 1986, to H. Forslund, details "Installation for Stacking Piles of Lumber Separated by Sticks". The device includes a number of sink compartments adapted to receive various types of lumber and a lumber conveyor designed to bring lumber from a loading point for unsorted lumber to the sink department. The lumber conveyor also transports sticks to the sink compartment for separation of the lumber in stacked tiers. A "Sticker Placer Apparatus" is detailed in U.S. Pat. No. 4,801,233, dated Jan. 31, 1989, to Edward Ritola. The apparatus includes multiple inclined sticker feed pockets designed to hold facing sticks and adapted to displace one stick at a time from the mouth of the sticker pocket to a variable height of lumber beneath the pocket. U.S. Pat. No. 4,810,152, dated Mar. 7, 1989, to Larry A. Gillingham, et al, details a "Sticker Positioning Apparatus for Use With Lumber Stacker". This apparatus includes an unscrambling conveyor that feeds six spacers from a bulk supply to a crowder feed conveyor, in order to supply sticks to a timed release mechanism. The release mechanism is operated by a cam device to sequentially present the individual spacer sticks in timed fashion to an endless distribution conveyor, where they are moved to the top of a lumber stack and accurately positioned in spaced relationship on the lumber. "A Stick Delivery Apparatus" is detailed in U.S. Pat. No. 4,878,803, dated Nov. 7, 1989, to Wade Q. Whiddon. The device includes a frame, a stick conveyor supported on the frame for movement between a stick supply station and a stick transfer station. The stick conveyor includes structure for transporting sticks from the supply station and for delivering the sticks to the transfer station in spaced, parallel relationship and additional apparatus is provided for replacing the sticks on stacked lumber beneath the frame.
It is an object of this invention to provide an automatic stick laying apparatus for mounting over stacks of lumber, plywood or pressboard and automatically placing spacing sticks on each successive layer of lumber, plywood or pressboard in spaced relationship to facilitate drying or other disposition of the lumber, plywood or pressboard.
Another object of this invention is to provide an automatic stick laying apparatus which is characterized by a fixed frame, a carriage assembly vertically slidably mounted on the fixed frame and fitted with parallel chain channels provided with positioner chains having spaced chain cleats for receiving spacing sticks and further including multiple diverter assemblies attached to the chain channels for sequentially displacing the spacing sticks from the chain cleats and locating the spacing sticks in selectively spaced relationship on successive stacks of lumber located beneath the stick laying apparatus.
Yet another object of this invention is to provide an automatic, computer-operated stick laying apparatus which utilizes a pair of vertically adjustable chain channels carrying positioner chains fitted with spaced chain cleats and a pair of companion advancing chains, for carrying spacing sticks into proper positions above stacked tiers of lumber located beneath the stick laying apparatus and diverter assemblies located between the chain channels for displacing the spacing sticks in a selected spacing on successive layers of lumber to space the layers of lumber for drying purposes.
Still another object of this invention is to provide a method for automatically placing spacing sticks on successive tiers of wood products such as lumber, plywood or the like, which method includes the steps of placing the spacing sticks between parallel sets of spaced cleats attached to a pair of positioner chains located above the lumber, locating the spacing sticks in proper positions over the lumber by operation of the positioner chains, lowering the positioner chains and spacing sticks to a point immediately above the top layer of lumber, causing the spacing sticks to be displaced in a selected sequence from the cleats to the lumber by operation of computerized diverter assemblies, raising the positioner chains and repositioning the diverter assemblies.